First of all, remember to change the bulbs about once a year, which is about 70% of the life of the bulbs. The light is most intense towards the center of a fluorescent bulb. Place your orchids as close as you can to the bulbs without touching the bulb. Follow the natural seasons. As I said above, in winter orchids need about 12 - 14 hours of light and in summer 16 hours is better. Don't just leave the lights on 24 hours a day thinking "the more the better."